Received Ticket from Apple: Most content doesn't show up in portrait view. I use IBA!

I received a ticket about most of my content not showing up in portrait mode, I don't understand how to fix it. I use IBA, and I have not had this problem with any of my previous three books. The only thing I've added was extra pictures, and two audio files, could this have broken it? I can't figure out how to fix the issue! When I look in landscape mode, everything shows up flawlessly, but in portrait mode it is an unmitigated mess, and only shows two of my pages, the first and the last, completely skipping the middle!